We propose to conduct a prospective randomized controlled trial comparing the cyclooxygenase-2 (COX-2) inhibitor celecoxib, in combination with endoscopic thermal ablation of Barrett's esophagus, to placebo and thermal ablation. COX-2 is overexpressed in Barrett's metaplasia. In this double-blind trial, 20 patients will be randomized to celecoxib or placebo (ratio 1:1) immediately following ablation. Celecoxib will be administered orally; 200 mg twice per day; the dose schedule for the placebo will be the same. Thermal ablation of Barrett's metaplasia will be carried out during endoscopy using argon plasma coagulation. Medication will be continued for one year, at which time a second endoscopy will be carried out to assess the outcomes. Endoscopic mapping of the Barrett's areas will be carried out at baseline and at one year. Primary study outcomes will be the comparison of the area of recurrent Barrett's metaplasia after ablation in the patients receiving celecoxib versus those receiving placebo, and the comparison of adverse events in the two treatment groups. Secondary outcomes will include change from baseline for the following measures in tissue samples from the treated areas: COX-2 mRNA, p53, cyclin D-1, Ki-67, and TUNEL assay. Eligible individuals will have an established diagnosis of Barrett's metaplasia without dysplasia. Individuals who have used corticosteroids or non-steroidal anti-inflammatory drugs (NSAIDs) chronically (except for low dose aspirin equal to < 100 mg/day) will not be eligible. Patients will be accrued during the first study year, and will be followed until the last patient enrolled completes one year of treatment.